1. Technical Field
The present invention relates to a semiconductor device having, in a case, a circuit formation region including a plurality of semiconductor elements, and to a method of manufacturing the semiconductor device, and particularly, relates to a semiconductor device wherein a plurality of semiconductor elements is electrically connected from wiring terminal plates embedded in the case through external connection terminal plates to external terminals formed on an outer peripheral portion of the case, and to a method of manufacturing the semiconductor device.
2. Related Art
In recent years, a reduction in size and weight of an inverter circuit which converts high electric power using a plurality of semiconductor elements such as insulated gate bipolar transistors (IGBTs) has been attempted. There is a description of a semiconductor device, such as a power module using a common IGBT module, in JP-A-08-148645 (for example, refer to paragraph number [0003] and FIG. 1).
That is, firstly, semiconductor chips such as IGBTs or diode chips are connected by a solder or the like to copper patterns formed on an insulating substrate, and furthermore, the insulating substrate is connected to a cooling base plate. Subsequently, a predetermined case is mounted around the cooling base plate, and electrodes of the semiconductor chips and the copper patterns on the insulating substrate are connected to metal terminal plates incorporated in the case by bonding aluminum wires in order to make an electrical connection between the metal terminal plates and the electrodes and copper patterns. An outer enclosing case, made of a thermoplastic resin, which encloses the insulating substrate is fixed to the cooling base plate with an adhesive, and furthermore, in order to protect the semiconductor chips and the bonded aluminum wires, an insulating material such as gel or epoxy resin is injected into the case, and hardened. Finally, external connection terminal plates are connected to the metal terminal plates incorporated in the case and external terminals by a laser welding, or the like, in order to make a connection between the metal terminal plates and external terminals.
Also, JP-A-2009-141000 (for example, refer to paragraph numbers [0024] to [0042] and FIG. 1) discloses a semiconductor device having a plurality of semiconductor elements encompassed by a resin case, wherein the disposition of wiring terminals can be easily changed. The semiconductor device includes a plurality of external connection terminals fixed and supported in the resin case, at least one semiconductor element encompassed in the resin case, and at least one terminal block on which is disposed at least one wiring terminal which electrically connects the semiconductor element and external connection terminal. With the semiconductor device, as the external connection terminals fixed in the resin case and metal foils are electrically connected through the terminal blocks, it is possible to easily implement a routing of the wiring terminals in the resin case. Also, even in the event that the external connection terminals are fixed and supported in the resin case, it is possible to freely change the disposition of the wiring terminals routed from the external connection terminals by preparing in advance some kinds of terminal block with the wiring terminals changed in wiring pattern.
Furthermore, a semiconductor device in JP-A-2010-103343 (for example, refer to paragraph numbers [0009] to [0037] and FIGS. 1 and 2) includes a resin case, semiconductor elements housed in the resin case, a printed circuit board, housed in the resin case, which includes control units controlling actions of the semiconductor elements, and a cover portion which covers the semiconductor elements and printed circuit board housed in the resin case, wherein an outer periphery of the printed circuit board is sandwiched by the resin case and cover portion. With this kind of configuration, it is possible to form a highly reliable semiconductor device having sufficient resistance to a vibration from outside and a cold and hot cycle.    Patent Document 1: Japanese Unexamined Patent Publication No. H08-148645    Patent Document 2: Japanese Unexamined Patent Publication No. 2009-141000    Patent Document 3: Japanese Unexamined Patent Publication No. 2010-1003343
With the configuration of a heretofore known semiconductor device, it is desired that the size of a case is reduced, and at the same time that the shape and size of the case, the positions of external terminals, and the like, can be freely determined in accordance with a demand from a user. In this case, it is not preferable from, the standpoint of the semiconductor device design to eject external connection terminals directly from semiconductor chips sealed inside the case.
Therefore, as shown in the heretofore described JP-A-2009-141000, a configuration wherein the semiconductor elements are electrically connected via internal connection wiring terminals to the external connection terminals disposed on an outer peripheral portion of the case is adopted. However, in a semiconductor device requiring a plurality of external connection terminals as in an IGBT module, the terminals must be spaced at a certain distance apart from each other in order to ensure insulation between the terminals. For this reason, in a semiconductor device with a configuration wherein a plurality of internal wiring terminal plates is connected to the external connection terminals inside a case, there has been a need to increase the size of the case itself to a certain degree.
In response to this, it is possible to reduce the size of the case by the internal wiring terminal plates being led outside the case in advance, and the internal wiring terminal plates and external connection terminals being rigidly connected outside the case by a laser welding. However, when the connections of the internal wiring terminal plates are exposed outside the case, the connections are likely to deteriorate in joint strength. For this reason, a heretofore known arrangement has been such that the joint strength is secured by increasing the welding area of laser welded portions, and at the same time, the connections are also prevented from deteriorating due to heat generated in semiconductor chips. Also, in order to maintain the insulation between the wiring terminal plates led outside the case, the junctions of the wiring terminal plates must be widely spaced apart from each other.